fs/jbd2/commit.c

   1 /*
   2  * linux/fs/jbd2/commit.c
   3  *
   4  * Written by Stephen C. Tweedie <sct@redhat.com>, 1998
   5  *
   6  * Copyright 1998 Red Hat corp --- All Rights Reserved
   7  *
   8  * This file is part of the Linux kernel and is made available under
   9  * the terms of the GNU General Public License, version 2, or at your
  10  * option, any later version, incorporated herein by reference.
  11  *
  12  * Journal commit routines for the generic filesystem journaling code;
  13  * part of the ext2fs journaling system.
  14  */
  15
  16 #include <linux/time.h>
  17 #include <linux/fs.h>
  18 #include <linux/jbd2.h>
  19 #include <linux/errno.h>
  20 #include <linux/slab.h>
  21 #include <linux/mm.h>
  22 #include <linux/pagemap.h>
  23 #include <linux/jiffies.h>
  24 #include <linux/crc32.h>
  25 #include <linux/writeback.h>
  26 #include <linux/backing-dev.h>
  27 #include <linux/bio.h>
  28 #include <linux/blkdev.h>
  29 #include <linux/bitops.h>
  30 #include <trace/events/jbd2.h>
  31 #include <asm/system.h>
  32
  33 /*
  34  * Default IO end handler for temporary BJ_IO buffer_heads.
  35  */
  36 static void journal_end_buffer_io_sync(struct buffer_head *bh, int uptodate)
  37 {
  38         BUFFER_TRACE(bh, "");
  39         if (uptodate)
  40                 set_buffer_uptodate(bh);
  41         else
  42                 clear_buffer_uptodate(bh);
  43         unlock_buffer(bh);
  44 }
  45
  46 /*
  47  * When an ext4 file is truncated, it is possible that some pages are not
  48  * successfully freed, because they are attached to a committing transaction.
  49  * After the transaction commits, these pages are left on the LRU, with no
  50  * ->mapping, and with attached buffers.  These pages are trivially reclaimable
  51  * by the VM, but their apparent absence upsets the VM accounting, and it makes
  52  * the numbers in /proc/meminfo look odd.
  53  *
  54  * So here, we have a buffer which has just come off the forget list.  Look to
  55  * see if we can strip all buffers from the backing page.
  56  *
  57  * Called under lock_journal(), and possibly under journal_datalist_lock.  The
  58  * caller provided us with a ref against the buffer, and we drop that here.
  59  */
  60 static void release_buffer_page(struct buffer_head *bh)
  61 {
  62         struct page *page;
  63
  64         if (buffer_dirty(bh))
  65                 goto nope;
  66         if (atomic_read(&bh->b_count) != 1)
  67                 goto nope;
  68         page = bh->b_page;
  69         if (!page)
  70                 goto nope;
  71         if (page->mapping)
  72                 goto nope;
  73
  74         /* OK, it's a truncated page */
  75         if (!trylock_page(page))
  76                 goto nope;
  77
  78         page_cache_get(page);
  79         __brelse(bh);
  80         try_to_free_buffers(page);
  81         unlock_page(page);
  82         page_cache_release(page);
  83         return;
  84
  85 nope:
  86         __brelse(bh);
  87 }
  88
  89 /*
  90  * Done it all: now submit the commit record.  We should have
  91  * cleaned up our previous buffers by now, so if we are in abort
  92  * mode we can now just skip the rest of the journal write
  93  * entirely.
  94  *
  95  * Returns 1 if the journal needs to be aborted or 0 on success
  96  */
  97 static int journal_submit_commit_record(journal_t *journal,
  98                                         transaction_t *commit_transaction,
  99                                         struct buffer_head **cbh,
 100                                         __u32 crc32_sum)
 101 {
 102         struct journal_head *descriptor;
 103         struct commit_header *tmp;
 104         struct buffer_head *bh;
 105         int ret;
 106         struct timespec now = current_kernel_time();
 107
 108         *cbh = NULL;
 109
 110         if (is_journal_aborted(journal))
 111                 return 0;
 112
 113         descriptor = jbd2_journal_get_descriptor_buffer(journal);
 114         if (!descriptor)
 115                 return 1;
 116
 117         bh = jh2bh(descriptor);
 118
 119         tmp = (struct commit_header *)bh->b_data;
 120         tmp->h_magic = cpu_to_be32(JBD2_MAGIC_NUMBER);
 121         tmp->h_blocktype = cpu_to_be32(JBD2_COMMIT_BLOCK);
 122         tmp->h_sequence = cpu_to_be32(commit_transaction->t_tid);
 123         tmp->h_commit_sec = cpu_to_be64(now.tv_sec);
 124         tmp->h_commit_nsec = cpu_to_be32(now.tv_nsec);
 125
 126         if (JBD2_HAS_COMPAT_FEATURE(journal,
 127                                     JBD2_FEATURE_COMPAT_CHECKSUM)) {
 128                 tmp->h_chksum_type      = JBD2_CRC32_CHKSUM;
 129                 tmp->h_chksum_size      = JBD2_CRC32_CHKSUM_SIZE;
 130                 tmp->h_chksum[0]        = cpu_to_be32(crc32_sum);
 131         }
 132
 133         JBUFFER_TRACE(descriptor, "submit commit block");
 134         lock_buffer(bh);
 135         clear_buffer_dirty(bh);
 136         set_buffer_uptodate(bh);
 137         bh->b_end_io = journal_end_buffer_io_sync;
 138
 139         if (journal->j_flags & JBD2_BARRIER &&
 140             !JBD2_HAS_INCOMPAT_FEATURE(journal,
 141                                        JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT))
 142                 ret = submit_bh(WRITE_SYNC | WRITE_FLUSH_FUA, bh);
 143         else
 144                 ret = submit_bh(WRITE_SYNC, bh);
 145
 146         *cbh = bh;
 147         return ret;
 148 }
 149
 150 /*
 151  * This function along with journal_submit_commit_record
 152  * allows to write the commit record asynchronously.
 153  */
 154 static int journal_wait_on_commit_record(journal_t *journal,
 155                                          struct buffer_head *bh)
 156 {
 157         int ret = 0;
 158
 159         clear_buffer_dirty(bh);
 160         wait_on_buffer(bh);
 161
 162         if (unlikely(!buffer_uptodate(bh)))
 163                 ret = -EIO;
 164         put_bh(bh);            /* One for getblk() */
 165         jbd2_journal_put_journal_head(bh2jh(bh));
 166
 167         return ret;
 168 }
 169
 170 /*
 171  * write the filemap data using writepage() address_space_operations.
 172  * We don't do block allocation here even for delalloc. We don't
 173  * use writepages() because with dealyed allocation we may be doing
 174  * block allocation in writepages().
 175  */
 176 static int journal_submit_inode_data_buffers(struct address_space *mapping)
 177 {
 178         int ret;
 179         struct writeback_control wbc = {
 180                 .sync_mode =  WB_SYNC_ALL,
 181                 .nr_to_write = mapping->nrpages * 2,
 182                 .range_start = 0,
 183                 .range_end = i_size_read(mapping->host),
 184         };
 185
 186         ret = generic_writepages(mapping, &wbc);
 187         return ret;
 188 }
 189
 190 /*
 191  * Submit all the data buffers of inode associated with the transaction to
 192  * disk.
 193  *
 194  * We are in a committing transaction. Therefore no new inode can be added to
 195  * our inode list. We use JI_COMMIT_RUNNING flag to protect inode we currently
 196  * operate on from being released while we write out pages.
 197  */
 198 static int journal_submit_data_buffers(journal_t *journal,
 199                 transaction_t *commit_transaction)
 200 {
 201         struct jbd2_inode *jinode;
 202         int err, ret = 0;
 203         struct address_space *mapping;
 204
 205         spin_lock(&journal->j_list_lock);
 206         list_for_each_entry(jinode, &commit_transaction->t_inode_list, i_list) {
 207                 mapping = jinode->i_vfs_inode->i_mapping;
 208                 set_bit(__JI_COMMIT_RUNNING, &jinode->i_flags);
 209                 spin_unlock(&journal->j_list_lock);
 210                 /*
 211                  * submit the inode data buffers. We use writepage
 212                  * instead of writepages. Because writepages can do
 213                  * block allocation  with delalloc. We need to write
 214                  * only allocated blocks here.
 215                  */
 216                 trace_jbd2_submit_inode_data(jinode->i_vfs_inode);
 217                 err = journal_submit_inode_data_buffers(mapping);
 218                 if (!ret)
 219                         ret = err;
 220                 spin_lock(&journal->j_list_lock);
 221                 J_ASSERT(jinode->i_transaction == commit_transaction);
 222                 commit_transaction->t_flushed_data_blocks = 1;
 223                 clear_bit(__JI_COMMIT_RUNNING, &jinode->i_flags);
 224                 smp_mb__after_clear_bit();
 225                 wake_up_bit(&jinode->i_flags, __JI_COMMIT_RUNNING);
 226         }
 227         spin_unlock(&journal->j_list_lock);
 228         return ret;
 229 }
 230
 231 /*
 232  * Wait for data submitted for writeout, refile inodes to proper
 233  * transaction if needed.
 234  *
 235  */
 236 static int journal_finish_inode_data_buffers(journal_t *journal,
 237                 transaction_t *commit_transaction)
 238 {
 239         struct jbd2_inode *jinode, *next_i;
 240         int err, ret = 0;
 241
 242         /* For locking, see the comment in journal_submit_data_buffers() */
 243         spin_lock(&journal->j_list_lock);
 244         list_for_each_entry(jinode, &commit_transaction->t_inode_list, i_list) {
 245                 set_bit(__JI_COMMIT_RUNNING, &jinode->i_flags);
 246                 spin_unlock(&journal->j_list_lock);
 247                 err = filemap_fdatawait(jinode->i_vfs_inode->i_mapping);
 248                 if (err) {
 249                         /*
 250                          * Because AS_EIO is cleared by
 251                          * filemap_fdatawait_range(), set it again so
 252                          * that user process can get -EIO from fsync().
 253                          */
 254                         set_bit(AS_EIO,
 255                                 &jinode->i_vfs_inode->i_mapping->flags);
 256
 257                         if (!ret)
 258                                 ret = err;
 259                 }
 260                 spin_lock(&journal->j_list_lock);
 261                 clear_bit(__JI_COMMIT_RUNNING, &jinode->i_flags);
 262                 smp_mb__after_clear_bit();
 263                 wake_up_bit(&jinode->i_flags, __JI_COMMIT_RUNNING);
 264         }
 265
 266         /* Now refile inode to proper lists */
 267         list_for_each_entry_safe(jinode, next_i,
 268                                  &commit_transaction->t_inode_list, i_list) {
 269                 list_del(&jinode->i_list);
 270                 if (jinode->i_next_transaction) {
 271                         jinode->i_transaction = jinode->i_next_transaction;
 272                         jinode->i_next_transaction = NULL;
 273                         list_add(&jinode->i_list,
 274                                 &jinode->i_transaction->t_inode_list);
 275                 } else {
 276                         jinode->i_transaction = NULL;
 277                 }
 278         }
 279         spin_unlock(&journal->j_list_lock);
 280
 281         return ret;
 282 }
 283
 284 static __u32 jbd2_checksum_data(__u32 crc32_sum, struct buffer_head *bh)
 285 {
 286         struct page *page = bh->b_page;
 287         char *addr;
 288         __u32 checksum;
 289
 290         addr = kmap_atomic(page, KM_USER0);
 291         checksum = crc32_be(crc32_sum,
 292                 (void *)(addr + offset_in_page(bh->b_data)), bh->b_size);
 293         kunmap_atomic(addr, KM_USER0);
 294
 295         return checksum;
 296 }
 297
 298 static void write_tag_block(int tag_bytes, journal_block_tag_t *tag,
 299                                    unsigned long long block)
 300 {
 301         tag->t_blocknr = cpu_to_be32(block & (u32)~0);
 302         if (tag_bytes > JBD2_TAG_SIZE32)
 303                 tag->t_blocknr_high = cpu_to_be32((block >> 31) >> 1);
 304 }
 305
 306 /*
 307  * jbd2_journal_commit_transaction
 308  *
 309  * The primary function for committing a transaction to the log.  This
 310  * function is called by the journal thread to begin a complete commit.
 311  */
 312 void jbd2_journal_commit_transaction(journal_t *journal)
 313 {
 314         struct transaction_stats_s stats;
 315         transaction_t *commit_transaction;
 316         struct journal_head *jh, *new_jh, *descriptor;
 317         struct buffer_head **wbuf = journal->j_wbuf;
 318         int bufs;
 319         int flags;
 320         int err;
 321         unsigned long long blocknr;
 322         ktime_t start_time;
 323         u64 commit_time;
 324         char *tagp = NULL;
 325         journal_header_t *header;
 326         journal_block_tag_t *tag = NULL;
 327         int space_left = 0;
 328         int first_tag = 0;
 329         int tag_flag;
 330         int i, to_free = 0;
 331         int tag_bytes = journal_tag_bytes(journal);
 332         struct buffer_head *cbh = NULL; /* For transactional checksums */
 333         __u32 crc32_sum = ~0;
 334         struct blk_plug plug;
 335
 336         /*
 337          * First job: lock down the current transaction and wait for
 338          * all outstanding updates to complete.
 339          */
 340
 341 #ifdef COMMIT_STATS
 342         spin_lock(&journal->j_list_lock);
 343         summarise_journal_usage(journal);
 344         spin_unlock(&journal->j_list_lock);
 345 #endif
 346
 347         /* Do we need to erase the effects of a prior jbd2_journal_flush? */
 348         if (journal->j_flags & JBD2_FLUSHED) {
 349                 jbd_debug(3, "super block updated\n");
 350                 jbd2_journal_update_superblock(journal, 1);
 351         } else {
 352                 jbd_debug(3, "superblock not updated\n");
 353         }
 354
 355         J_ASSERT(journal->j_running_transaction != NULL);
 356         J_ASSERT(journal->j_committing_transaction == NULL);
 357
 358         commit_transaction = journal->j_running_transaction;
 359         J_ASSERT(commit_transaction->t_state == T_RUNNING);
 360
 361         trace_jbd2_start_commit(journal, commit_transaction);
 362         jbd_debug(1, "JBD: starting commit of transaction %d\n",
 363                         commit_transaction->t_tid);
 364
 365         write_lock(&journal->j_state_lock);
 366         commit_transaction->t_state = T_LOCKED;
 367
 368         trace_jbd2_commit_locking(journal, commit_transaction);
 369         stats.run.rs_wait = commit_transaction->t_max_wait;
 370         stats.run.rs_locked = jiffies;
 371         stats.run.rs_running = jbd2_time_diff(commit_transaction->t_start,
 372                                               stats.run.rs_locked);
 373
 374         spin_lock(&commit_transaction->t_handle_lock);
 375         while (atomic_read(&commit_transaction->t_updates)) {
 376                 DEFINE_WAIT(wait);
 377
 378                 prepare_to_wait(&journal->j_wait_updates, &wait,
 379                                         TASK_UNINTERRUPTIBLE);
 380                 if (atomic_read(&commit_transaction->t_updates)) {
 381                         spin_unlock(&commit_transaction->t_handle_lock);
 382                         write_unlock(&journal->j_state_lock);
 383                         schedule();
 384                         write_lock(&journal->j_state_lock);
 385                         spin_lock(&commit_transaction->t_handle_lock);
 386                 }
 387                 finish_wait(&journal->j_wait_updates, &wait);
 388         }
 389         spin_unlock(&commit_transaction->t_handle_lock);
 390
 391         J_ASSERT (atomic_read(&commit_transaction->t_outstanding_credits) <=
 392                         journal->j_max_transaction_buffers);
 393
 394         /*
 395          * First thing we are allowed to do is to discard any remaining
 396          * BJ_Reserved buffers.  Note, it is _not_ permissible to assume
 397          * that there are no such buffers: if a large filesystem
 398          * operation like a truncate needs to split itself over multiple
 399          * transactions, then it may try to do a jbd2_journal_restart() while
 400          * there are still BJ_Reserved buffers outstanding.  These must
 401          * be released cleanly from the current transaction.
 402          *
 403          * In this case, the filesystem must still reserve write access
 404          * again before modifying the buffer in the new transaction, but
 405          * we do not require it to remember exactly which old buffers it
 406          * has reserved.  This is consistent with the existing behaviour
 407          * that multiple jbd2_journal_get_write_access() calls to the same
 408          * buffer are perfectly permissible.
 409          */
 410         while (commit_transaction->t_reserved_list) {
 411                 jh = commit_transaction->t_reserved_list;
 412                 JBUFFER_TRACE(jh, "reserved, unused: refile");
 413                 /*
 414                  * A jbd2_journal_get_undo_access()+jbd2_journal_release_buffer() may
 415                  * leave undo-committed data.
 416                  */
 417                 if (jh->b_committed_data) {
 418                         struct buffer_head *bh = jh2bh(jh);
 419
 420                         jbd_lock_bh_state(bh);
 421                         jbd2_free(jh->b_committed_data, bh->b_size);
 422                         jh->b_committed_data = NULL;
 423                         jbd_unlock_bh_state(bh);
 424                 }
 425                 jbd2_journal_refile_buffer(journal, jh);
 426         }
 427
 428         /*
 429          * Now try to drop any written-back buffers from the journal's
 430          * checkpoint lists.  We do this *before* commit because it potentially
 431          * frees some memory
 432          */
 433         spin_lock(&journal->j_list_lock);
 434         __jbd2_journal_clean_checkpoint_list(journal);
 435         spin_unlock(&journal->j_list_lock);
 436
 437         jbd_debug (3, "JBD: commit phase 1\n");
 438
 439         /*
 440          * Switch to a new revoke table.
 441          */
 442         jbd2_journal_switch_revoke_table(journal);
 443
 444         trace_jbd2_commit_flushing(journal, commit_transaction);
 445         stats.run.rs_flushing = jiffies;
 446         stats.run.rs_locked = jbd2_time_diff(stats.run.rs_locked,
 447                                              stats.run.rs_flushing);
 448
 449         commit_transaction->t_state = T_FLUSH;
 450         journal->j_committing_transaction = commit_transaction;
 451         journal->j_running_transaction = NULL;
 452         start_time = ktime_get();
 453         commit_transaction->t_log_start = journal->j_head;
 454         wake_up(&journal->j_wait_transaction_locked);
 455         write_unlock(&journal->j_state_lock);
 456
 457         jbd_debug (3, "JBD: commit phase 2\n");
 458
 459         /*
 460          * Now start flushing things to disk, in the order they appear
 461          * on the transaction lists.  Data blocks go first.
 462          */
 463         err = journal_submit_data_buffers(journal, commit_transaction);
 464         if (err)
 465                 jbd2_journal_abort(journal, err);
 466
 467         blk_start_plug(&plug);
 468         jbd2_journal_write_revoke_records(journal, commit_transaction,
 469                                           WRITE_SYNC);
 470         blk_finish_plug(&plug);
 471
 472         jbd_debug(3, "JBD: commit phase 2\n");
 473
 474         /*
 475          * Way to go: we have now written out all of the data for a
 476          * transaction!  Now comes the tricky part: we need to write out
 477          * metadata.  Loop over the transaction's entire buffer list:
 478          */
 479         write_lock(&journal->j_state_lock);
 480         commit_transaction->t_state = T_COMMIT;
 481         write_unlock(&journal->j_state_lock);
 482
 483         trace_jbd2_commit_logging(journal, commit_transaction);
 484         stats.run.rs_logging = jiffies;
 485         stats.run.rs_flushing = jbd2_time_diff(stats.run.rs_flushing,
 486                                                stats.run.rs_logging);
 487         stats.run.rs_blocks =
 488                 atomic_read(&commit_transaction->t_outstanding_credits);
 489         stats.run.rs_blocks_logged = 0;
 490
 491         J_ASSERT(commit_transaction->t_nr_buffers <=
 492                  atomic_read(&commit_transaction->t_outstanding_credits));
 493
 494         err = 0;
 495         descriptor = NULL;
 496         bufs = 0;
 497         blk_start_plug(&plug);
 498         while (commit_transaction->t_buffers) {
 499
 500                 /* Find the next buffer to be journaled... */
 501
 502                 jh = commit_transaction->t_buffers;
 503
 504                 /* If we're in abort mode, we just un-journal the buffer and
 505                    release it. */
 506
 507                 if (is_journal_aborted(journal)) {
 508                         clear_buffer_jbddirty(jh2bh(jh));
 509                         JBUFFER_TRACE(jh, "journal is aborting: refile");
 510                         jbd2_buffer_abort_trigger(jh,
 511                                                   jh->b_frozen_data ?
 512                                                   jh->b_frozen_triggers :
 513                                                   jh->b_triggers);
 514                         jbd2_journal_refile_buffer(journal, jh);
 515                         /* If that was the last one, we need to clean up
 516                          * any descriptor buffers which may have been
 517                          * already allocated, even if we are now
 518                          * aborting. */
 519                         if (!commit_transaction->t_buffers)
 520                                 goto start_journal_io;
 521                         continue;
 522                 }
 523
 524                 /* Make sure we have a descriptor block in which to
 525                    record the metadata buffer. */
 526
 527                 if (!descriptor) {
 528                         struct buffer_head *bh;
 529
 530                         J_ASSERT (bufs == 0);
 531
 532                         jbd_debug(4, "JBD: get descriptor\n");
 533
 534                         descriptor = jbd2_journal_get_descriptor_buffer(journal);
 535                         if (!descriptor) {
 536                                 jbd2_journal_abort(journal, -EIO);
 537                                 continue;
 538                         }
 539
 540                         bh = jh2bh(descriptor);
 541                         jbd_debug(4, "JBD: got buffer %llu (%p)\n",
 542                                 (unsigned long long)bh->b_blocknr, bh->b_data);
 543                         header = (journal_header_t *)&bh->b_data[0];
 544                         header->h_magic     = cpu_to_be32(JBD2_MAGIC_NUMBER);
 545                         header->h_blocktype = cpu_to_be32(JBD2_DESCRIPTOR_BLOCK);
 546                         header->h_sequence  = cpu_to_be32(commit_transaction->t_tid);
 547
 548                         tagp = &bh->b_data[sizeof(journal_header_t)];
 549                         space_left = bh->b_size - sizeof(journal_header_t);
 550                         first_tag = 1;
 551                         set_buffer_jwrite(bh);
 552                         set_buffer_dirty(bh);
 553                         wbuf[bufs++] = bh;
 554
 555                         /* Record it so that we can wait for IO
 556                            completion later */
 557                         BUFFER_TRACE(bh, "ph3: file as descriptor");
 558                         jbd2_journal_file_buffer(descriptor, commit_transaction,
 559                                         BJ_LogCtl);
 560                 }
 561
 562                 /* Where is the buffer to be written? */
 563
 564                 err = jbd2_journal_next_log_block(journal, &blocknr);
 565                 /* If the block mapping failed, just abandon the buffer
 566                    and repeat this loop: we'll fall into the
 567                    refile-on-abort condition above. */
 568                 if (err) {
 569                         jbd2_journal_abort(journal, err);
 570                         continue;
 571                 }
 572
 573                 /*
 574                  * start_this_handle() uses t_outstanding_credits to determine
 575                  * the free space in the log, but this counter is changed
 576                  * by jbd2_journal_next_log_block() also.
 577                  */
 578                 atomic_dec(&commit_transaction->t_outstanding_credits);
 579
 580                 /* Bump b_count to prevent truncate from stumbling over
 581                    the shadowed buffer!  @@@ This can go if we ever get
 582                    rid of the BJ_IO/BJ_Shadow pairing of buffers. */
 583                 atomic_inc(&jh2bh(jh)->b_count);
 584
 585                 /* Make a temporary IO buffer with which to write it out
 586                    (this will requeue both the metadata buffer and the
 587                    temporary IO buffer). new_bh goes on BJ_IO*/
 588
 589                 set_bit(BH_JWrite, &jh2bh(jh)->b_state);
 590                 /*
 591                  * akpm: jbd2_journal_write_metadata_buffer() sets
 592                  * new_bh->b_transaction to commit_transaction.
 593                  * We need to clean this up before we release new_bh
 594                  * (which is of type BJ_IO)
 595                  */
 596                 JBUFFER_TRACE(jh, "ph3: write metadata");
 597                 flags = jbd2_journal_write_metadata_buffer(commit_transaction,
 598                                                       jh, &new_jh, blocknr);
 599                 if (flags < 0) {
 600                         jbd2_journal_abort(journal, flags);
 601                         continue;
 602                 }
 603                 set_bit(BH_JWrite, &jh2bh(new_jh)->b_state);
 604                 wbuf[bufs++] = jh2bh(new_jh);
 605
 606                 /* Record the new block's tag in the current descriptor
 607                    buffer */
 608
 609                 tag_flag = 0;
 610                 if (flags & 1)
 611                         tag_flag |= JBD2_FLAG_ESCAPE;
 612                 if (!first_tag)
 613                         tag_flag |= JBD2_FLAG_SAME_UUID;
 614
 615                 tag = (journal_block_tag_t *) tagp;
 616                 write_tag_block(tag_bytes, tag, jh2bh(jh)->b_blocknr);
 617                 tag->t_flags = cpu_to_be32(tag_flag);
 618                 tagp += tag_bytes;
 619                 space_left -= tag_bytes;
 620
 621                 if (first_tag) {
 622                         memcpy (tagp, journal->j_uuid, 16);
 623                         tagp += 16;
 624                         space_left -= 16;
 625                         first_tag = 0;
 626                 }
 627
 628                 /* If there's no more to do, or if the descriptor is full,
 629                    let the IO rip! */
 630
 631                 if (bufs == journal->j_wbufsize ||
 632                     commit_transaction->t_buffers == NULL ||
 633                     space_left < tag_bytes + 16) {
 634
 635                         jbd_debug(4, "JBD: Submit %d IOs\n", bufs);
 636
 637                         /* Write an end-of-descriptor marker before
 638                            submitting the IOs.  "tag" still points to
 639                            the last tag we set up. */
 640
 641                         tag->t_flags |= cpu_to_be32(JBD2_FLAG_LAST_TAG);
 642
 643 start_journal_io:
 644                         for (i = 0; i < bufs; i++) {
 645                                 struct buffer_head *bh = wbuf[i];
 646                                 /*
 647                                  * Compute checksum.
 648                                  */
 649                                 if (JBD2_HAS_COMPAT_FEATURE(journal,
 650                                         JBD2_FEATURE_COMPAT_CHECKSUM)) {
 651                                         crc32_sum =
 652                                             jbd2_checksum_data(crc32_sum, bh);
 653                                 }
 654
 655                                 lock_buffer(bh);
 656                                 clear_buffer_dirty(bh);
 657                                 set_buffer_uptodate(bh);
 658                                 bh->b_end_io = journal_end_buffer_io_sync;
 659                                 submit_bh(WRITE_SYNC, bh);
 660                         }
 661                         cond_resched();
 662                         stats.run.rs_blocks_logged += bufs;
 663
 664                         /* Force a new descriptor to be generated next
 665                            time round the loop. */
 666                         descriptor = NULL;
 667                         bufs = 0;
 668                 }
 669         }
 670
 671         err = journal_finish_inode_data_buffers(journal, commit_transaction);
 672         if (err) {
 673                 printk(KERN_WARNING
 674                         "JBD2: Detected IO errors while flushing file data "
 675                        "on %s\n", journal->j_devname);
 676                 if (journal->j_flags & JBD2_ABORT_ON_SYNCDATA_ERR)
 677                         jbd2_journal_abort(journal, err);
 678                 err = 0;
 679         }
 680
 681         /*
 682          * If the journal is not located on the file system device,
 683          * then we must flush the file system device before we issue
 684          * the commit record
 685          */
 686         if (commit_transaction->t_flushed_data_blocks &&
 687             (journal->j_fs_dev != journal->j_dev) &&
 688             (journal->j_flags & JBD2_BARRIER))
 689                 blkdev_issue_flush(journal->j_fs_dev, GFP_KERNEL, NULL);
 690
 691         /* Done it all: now write the commit record asynchronously. */
 692         if (JBD2_HAS_INCOMPAT_FEATURE(journal,
 693                                       JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT)) {
 694                 err = journal_submit_commit_record(journal, commit_transaction,
 695                                                  &cbh, crc32_sum);
 696                 if (err)
 697                         __jbd2_journal_abort_hard(journal);
 698         }
 699
 700         blk_finish_plug(&plug);
 701
 702         /* Lo and behold: we have just managed to send a transaction to
 703            the log.  Before we can commit it, wait for the IO so far to
 704            complete.  Control buffers being written are on the
 705            transaction's t_log_list queue, and metadata buffers are on
 706            the t_iobuf_list queue.
 707
 708            Wait for the buffers in reverse order.  That way we are
 709            less likely to be woken up until all IOs have completed, and
 710            so we incur less scheduling load.
 711         */
 712
 713         jbd_debug(3, "JBD: commit phase 3\n");
 714
 715         /*
 716          * akpm: these are BJ_IO, and j_list_lock is not needed.
 717          * See __journal_try_to_free_buffer.
 718          */
 719 wait_for_iobuf:
 720         while (commit_transaction->t_iobuf_list != NULL) {
 721                 struct buffer_head *bh;
 722
 723                 jh = commit_transaction->t_iobuf_list->b_tprev;
 724                 bh = jh2bh(jh);
 725                 if (buffer_locked(bh)) {
 726                         wait_on_buffer(bh);
 727                         goto wait_for_iobuf;
 728                 }
 729                 if (cond_resched())
 730                         goto wait_for_iobuf;
 731
 732                 if (unlikely(!buffer_uptodate(bh)))
 733                         err = -EIO;
 734
 735                 clear_buffer_jwrite(bh);
 736
 737                 JBUFFER_TRACE(jh, "ph4: unfile after journal write");
 738                 jbd2_journal_unfile_buffer(journal, jh);
 739
 740                 /*
 741                  * ->t_iobuf_list should contain only dummy buffer_heads
 742                  * which were created by jbd2_journal_write_metadata_buffer().
 743                  */
 744                 BUFFER_TRACE(bh, "dumping temporary bh");
 745                 jbd2_journal_put_journal_head(jh);
 746                 __brelse(bh);
 747                 J_ASSERT_BH(bh, atomic_read(&bh->b_count) == 0);
 748                 free_buffer_head(bh);
 749
 750                 /* We also have to unlock and free the corresponding
 751                    shadowed buffer */
 752                 jh = commit_transaction->t_shadow_list->b_tprev;
 753                 bh = jh2bh(jh);
 754                 clear_bit(BH_JWrite, &bh->b_state);
 755                 J_ASSERT_BH(bh, buffer_jbddirty(bh));
 756
 757                 /* The metadata is now released for reuse, but we need
 758                    to remember it against this transaction so that when
 759                    we finally commit, we can do any checkpointing
 760                    required. */
 761                 JBUFFER_TRACE(jh, "file as BJ_Forget");
 762                 jbd2_journal_file_buffer(jh, commit_transaction, BJ_Forget);
 763                 /* Wake up any transactions which were waiting for this
 764                    IO to complete */
 765                 wake_up_bit(&bh->b_state, BH_Unshadow);
 766                 JBUFFER_TRACE(jh, "brelse shadowed buffer");
 767                 __brelse(bh);
 768         }
 769
 770         J_ASSERT (commit_transaction->t_shadow_list == NULL);
 771
 772         jbd_debug(3, "JBD: commit phase 4\n");
 773
 774         /* Here we wait for the revoke record and descriptor record buffers */
 775  wait_for_ctlbuf:
 776         while (commit_transaction->t_log_list != NULL) {
 777                 struct buffer_head *bh;
 778
 779                 jh = commit_transaction->t_log_list->b_tprev;
 780                 bh = jh2bh(jh);
 781                 if (buffer_locked(bh)) {
 782                         wait_on_buffer(bh);
 783                         goto wait_for_ctlbuf;
 784                 }
 785                 if (cond_resched())
 786                         goto wait_for_ctlbuf;
 787
 788                 if (unlikely(!buffer_uptodate(bh)))
 789                         err = -EIO;
 790
 791                 BUFFER_TRACE(bh, "ph5: control buffer writeout done: unfile");
 792                 clear_buffer_jwrite(bh);
 793                 jbd2_journal_unfile_buffer(journal, jh);
 794                 jbd2_journal_put_journal_head(jh);
 795                 __brelse(bh);           /* One for getblk */
 796                 /* AKPM: bforget here */
 797         }
 798
 799         if (err)
 800                 jbd2_journal_abort(journal, err);
 801
 802         jbd_debug(3, "JBD: commit phase 5\n");
 803
 804         if (!JBD2_HAS_INCOMPAT_FEATURE(journal,
 805                                        JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT)) {
 806                 err = journal_submit_commit_record(journal, commit_transaction,
 807                                                 &cbh, crc32_sum);
 808                 if (err)
 809                         __jbd2_journal_abort_hard(journal);
 810         }
 811         if (cbh)
 812                 err = journal_wait_on_commit_record(journal, cbh);
 813         if (JBD2_HAS_INCOMPAT_FEATURE(journal,
 814                                       JBD2_FEATURE_INCOMPAT_ASYNC_COMMIT) &&
 815             journal->j_flags & JBD2_BARRIER) {
 816                 blkdev_issue_flush(journal->j_dev, GFP_KERNEL, NULL);
 817         }
 818
 819         if (err)
 820                 jbd2_journal_abort(journal, err);
 821
 822         /* End of a transaction!  Finally, we can do checkpoint
 823            processing: any buffers committed as a result of this
 824            transaction can be removed from any checkpoint list it was on
 825            before. */
 826
 827         jbd_debug(3, "JBD: commit phase 6\n");
 828
 829         J_ASSERT(list_empty(&commit_transaction->t_inode_list));
 830         J_ASSERT(commit_transaction->t_buffers == NULL);
 831         J_ASSERT(commit_transaction->t_checkpoint_list == NULL);
 832         J_ASSERT(commit_transaction->t_iobuf_list == NULL);
 833         J_ASSERT(commit_transaction->t_shadow_list == NULL);
 834         J_ASSERT(commit_transaction->t_log_list == NULL);
 835
 836 restart_loop:
 837         /*
 838          * As there are other places (journal_unmap_buffer()) adding buffers
 839          * to this list we have to be careful and hold the j_list_lock.
 840          */
 841         spin_lock(&journal->j_list_lock);
 842         while (commit_transaction->t_forget) {
 843                 transaction_t *cp_transaction;
 844                 struct buffer_head *bh;
 845
 846                 jh = commit_transaction->t_forget;
 847                 spin_unlock(&journal->j_list_lock);
 848                 bh = jh2bh(jh);
 849                 jbd_lock_bh_state(bh);
 850                 J_ASSERT_JH(jh, jh->b_transaction == commit_transaction);
 851
 852                 /*
 853                  * If there is undo-protected committed data against
 854                  * this buffer, then we can remove it now.  If it is a
 855                  * buffer needing such protection, the old frozen_data
 856                  * field now points to a committed version of the
 857                  * buffer, so rotate that field to the new committed
 858                  * data.
 859                  *
 860                  * Otherwise, we can just throw away the frozen data now.
 861                  *
 862                  * We also know that the frozen data has already fired
 863                  * its triggers if they exist, so we can clear that too.
 864                  */
 865                 if (jh->b_committed_data) {
 866                         jbd2_free(jh->b_committed_data, bh->b_size);
 867                         jh->b_committed_data = NULL;
 868                         if (jh->b_frozen_data) {
 869                                 jh->b_committed_data = jh->b_frozen_data;
 870                                 jh->b_frozen_data = NULL;
 871                                 jh->b_frozen_triggers = NULL;
 872                         }
 873                 } else if (jh->b_frozen_data) {
 874                         jbd2_free(jh->b_frozen_data, bh->b_size);
 875                         jh->b_frozen_data = NULL;
 876                         jh->b_frozen_triggers = NULL;
 877                 }
 878
 879                 spin_lock(&journal->j_list_lock);
 880                 cp_transaction = jh->b_cp_transaction;
 881                 if (cp_transaction) {
 882                         JBUFFER_TRACE(jh, "remove from old cp transaction");
 883                         cp_transaction->t_chp_stats.cs_dropped++;
 884                         __jbd2_journal_remove_checkpoint(jh);
 885                 }
 886
 887                 /* Only re-checkpoint the buffer_head if it is marked
 888                  * dirty.  If the buffer was added to the BJ_Forget list
 889                  * by jbd2_journal_forget, it may no longer be dirty and
 890                  * there's no point in keeping a checkpoint record for
 891                  * it. */
 892
 893                 /* A buffer which has been freed while still being
 894                  * journaled by a previous transaction may end up still
 895                  * being dirty here, but we want to avoid writing back
 896                  * that buffer in the future after the "add to orphan"
 897                  * operation been committed,  That's not only a performance
 898                  * gain, it also stops aliasing problems if the buffer is
 899                  * left behind for writeback and gets reallocated for another
 900                  * use in a different page. */
 901                 if (buffer_freed(bh) && !jh->b_next_transaction) {
 902                         clear_buffer_freed(bh);
 903                         clear_buffer_jbddirty(bh);
 904                 }
 905
 906                 if (buffer_jbddirty(bh)) {
 907                         JBUFFER_TRACE(jh, "add to new checkpointing trans");
 908                         __jbd2_journal_insert_checkpoint(jh, commit_transaction);
 909                         if (is_journal_aborted(journal))
 910                                 clear_buffer_jbddirty(bh);
 911                         JBUFFER_TRACE(jh, "refile for checkpoint writeback");
 912                         __jbd2_journal_refile_buffer(jh);
 913                         jbd_unlock_bh_state(bh);
 914                 } else {
 915                         J_ASSERT_BH(bh, !buffer_dirty(bh));
 916                         /* The buffer on BJ_Forget list and not jbddirty means
 917                          * it has been freed by this transaction and hence it
 918                          * could not have been reallocated until this
 919                          * transaction has committed. *BUT* it could be
 920                          * reallocated once we have written all the data to
 921                          * disk and before we process the buffer on BJ_Forget
 922                          * list. */
 923                         JBUFFER_TRACE(jh, "refile or unfile freed buffer");
 924                         __jbd2_journal_refile_buffer(jh);
 925                         if (!jh->b_transaction) {
 926                                 jbd_unlock_bh_state(bh);
 927                                  /* needs a brelse */
 928                                 jbd2_journal_remove_journal_head(bh);
 929                                 release_buffer_page(bh);
 930                         } else
 931                                 jbd_unlock_bh_state(bh);
 932                 }
 933                 cond_resched_lock(&journal->j_list_lock);
 934         }
 935         spin_unlock(&journal->j_list_lock);
 936         /*
 937          * This is a bit sleazy.  We use j_list_lock to protect transition
 938          * of a transaction into T_FINISHED state and calling
 939          * __jbd2_journal_drop_transaction(). Otherwise we could race with
 940          * other checkpointing code processing the transaction...
 941          */
 942         write_lock(&journal->j_state_lock);
 943         spin_lock(&journal->j_list_lock);
 944         /*
 945          * Now recheck if some buffers did not get attached to the transaction
 946          * while the lock was dropped...
 947          */
 948         if (commit_transaction->t_forget) {
 949                 spin_unlock(&journal->j_list_lock);
 950                 write_unlock(&journal->j_state_lock);
 951                 goto restart_loop;
 952         }
 953
 954         /* Done with this transaction! */
 955
 956         jbd_debug(3, "JBD: commit phase 7\n");
 957
 958         J_ASSERT(commit_transaction->t_state == T_COMMIT);
 959
 960         commit_transaction->t_start = jiffies;
 961         stats.run.rs_logging = jbd2_time_diff(stats.run.rs_logging,
 962                                               commit_transaction->t_start);
 963
 964         /*
 965          * File the transaction statistics
 966          */
 967         stats.ts_tid = commit_transaction->t_tid;
 968         stats.run.rs_handle_count =
 969                 atomic_read(&commit_transaction->t_handle_count);
 970         trace_jbd2_run_stats(journal->j_fs_dev->bd_dev,
 971                              commit_transaction->t_tid, &stats.run);
 972
 973         /*
 974          * Calculate overall stats
 975          */
 976         spin_lock(&journal->j_history_lock);
 977         journal->j_stats.ts_tid++;
 978         journal->j_stats.run.rs_wait += stats.run.rs_wait;
 979         journal->j_stats.run.rs_running += stats.run.rs_running;
 980         journal->j_stats.run.rs_locked += stats.run.rs_locked;
 981         journal->j_stats.run.rs_flushing += stats.run.rs_flushing;
 982         journal->j_stats.run.rs_logging += stats.run.rs_logging;
 983         journal->j_stats.run.rs_handle_count += stats.run.rs_handle_count;
 984         journal->j_stats.run.rs_blocks += stats.run.rs_blocks;
 985         journal->j_stats.run.rs_blocks_logged += stats.run.rs_blocks_logged;
 986         spin_unlock(&journal->j_history_lock);
 987
 988         commit_transaction->t_state = T_FINISHED;
 989         J_ASSERT(commit_transaction == journal->j_committing_transaction);
 990         journal->j_commit_sequence = commit_transaction->t_tid;
 991         journal->j_committing_transaction = NULL;
 992         commit_time = ktime_to_ns(ktime_sub(ktime_get(), start_time));
 993
 994         /*
 995          * weight the commit time higher than the average time so we don't
 996          * react too strongly to vast changes in the commit time
 997          */
 998         if (likely(journal->j_average_commit_time))
 999                 journal->j_average_commit_time = (commit_time +
1000                                 journal->j_average_commit_time*3) / 4;
1001         else
1002                 journal->j_average_commit_time = commit_time;
1003         write_unlock(&journal->j_state_lock);
1004
1005         if (commit_transaction->t_checkpoint_list == NULL &&
1006             commit_transaction->t_checkpoint_io_list == NULL) {
1007                 __jbd2_journal_drop_transaction(journal, commit_transaction);
1008                 to_free = 1;
1009         } else {
1010                 if (journal->j_checkpoint_transactions == NULL) {
1011                         journal->j_checkpoint_transactions = commit_transaction;
1012                         commit_transaction->t_cpnext = commit_transaction;
1013                         commit_transaction->t_cpprev = commit_transaction;
1014                 } else {
1015                         commit_transaction->t_cpnext =
1016                                 journal->j_checkpoint_transactions;
1017                         commit_transaction->t_cpprev =
1018                                 commit_transaction->t_cpnext->t_cpprev;
1019                         commit_transaction->t_cpnext->t_cpprev =
1020                                 commit_transaction;
1021                         commit_transaction->t_cpprev->t_cpnext =
1022                                 commit_transaction;
1023                 }
1024         }
1025         spin_unlock(&journal->j_list_lock);
1026
1027         if (journal->j_commit_callback)
1028                 journal->j_commit_callback(journal, commit_transaction);
1029
1030         trace_jbd2_end_commit(journal, commit_transaction);
1031         jbd_debug(1, "JBD: commit %d complete, head %d\n",
1032                   journal->j_commit_sequence, journal->j_tail_sequence);
1033         if (to_free)
1034                 kfree(commit_transaction);
1035
1036         wake_up(&journal->j_wait_done_commit);
1037 }